A High Voltage Direct Current (HVDC) system supplies power by converting AC power from a power plant into DC power, transmitting the DC power, and then inverting the DC power into AC power at a power receiving point. The HVDC system has a loss of power less than an AC transmission type, so it has high power transmission efficiency. Further, the system can improve stability through line separation and has small inductive disturbance, so it is advantageous in long-distance power transmission.
The HVDC system is installed in a structure called a converter module composed of a plurality of submodules stacked 10 meters high in a plurality of layers. The submodules generate a large amount of heat during operation. Accordingly, many studies on structures for discharging heat generated by a submodule to the outside have been conducted. In particular, it is required to separate all components including a cable and a cooling water hose connected to a submodule in order to take down a submodule from a high position for maintenance on the ground.
However, cooling water that leaks while the cooling hose is separated from the submodule may flow into the submodule and may cause leakage of electricity or corrosion. This is because the cooling water hose extends into the submodule through the top of the submodule and water leaking from the cooling water hose can enter the submodule.
Further, the cooling water hose should be separated from the submodule to maintain the submodule, but it cannot, so the submodule should be moved together with the cooling water hose.
Furthermore, since the cooling water hose etc. are positioned over the submodule, it is difficult for a worker to work over the submodule.